diff options
| -rw-r--r-- | stand/common/bcache.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/stand/common/bcache.c b/stand/common/bcache.c index a020f3c3c53c..526f9fe3fa5c 100644 --- a/stand/common/bcache.c +++ b/stand/common/bcache.c @@ -66,6 +66,7 @@ struct bcache { caddr_t bcache_data; size_t bcache_nblks; size_t ra; + daddr_t bcache_nextblkno; }; static u_int bcache_total_nblks; /* set by bcache_init */ @@ -163,6 +164,7 @@ bcache_allocate(void) } bcache_units++; bc->ra = BCACHE_READAHEAD; /* optimistic read ahead */ + bc->bcache_nextblkno = -1; return (bc); } @@ -291,6 +293,14 @@ read_strategy(void *devdata, int rw, daddr_t blk, size_t size, else ra = bc->bcache_nblks - BHASH(bc, p_blk + p_size); + /* + * Only trigger read-ahead if we detect two blocks being read + * sequentially. + */ + if ((bc->bcache_nextblkno != blk) && ra != 0) { + ra = 0; + } + if (ra != 0 && ra != bc->bcache_nblks) { /* do we have RA space? */ ra = MIN(bc->ra, ra - 1); ra = rounddown(ra, 16); /* multiple of 16 blocks */ @@ -342,8 +352,11 @@ read_strategy(void *devdata, int rw, daddr_t blk, size_t size, } done: - if ((result == 0) && (rsize != NULL)) - *rsize = size; + if (result == 0) { + if (rsize != NULL) + *rsize = size; + bc->bcache_nextblkno = blk + (size / DEV_BSIZE); + } return(result); } |